Sterilants are used in many areas, such as in the sterilization of laboratory, surgical, dental and other equipment. It is convenient in hospital practice to sterilize instruments overnight, using chemical sterilizing agents or other sterilizing methods.
The most common methods of sterilization involve either the use of steam under pressure, dry heat or ethylene oxide. However, some of these methods can be cumbersome, tedious and time-consuming, often damage the sterilized material and require expensive equipment and skilled technicians.
The power of a chemical sterilizing agent is best measured by its ability to kill sporulating bacteria, while many disinfectants can kill vegetative bacteria, very few are capable of killing dormant spores, such as Bacillus subtilis, Bacillus pumilus, Clostridium sporogenes and Clostridium tetani.
The term "sterilizing composition" as used herein is intended to refer to compositions which are capable of killing dormant spores in addition to vegetative bacteria while the term "sterilizing" refers to the killing of dormant spores.
Some activity in the search for a more effective and convenient sterilizing procedure has been centered around the use of glutaraldehyde as the basis for chemical sterilant compositions.
Commercially-available glutaraldehyde is in the form of an acidic aqueous solution which is stable over long periods of time. However, these solutions do not exhibit the ability to kill dormant spores at room temperature (i.e., 20.degree. to 25.degree. C.) within an acceptable period of time, i.e., less than 16 hours (a period of time equivalent to an overnight treatment) and for even longer periods in excess of 24 hours. This acidic solution cannot therefore, be used as is as a sterilant composition.
U.S. Pat. No. 3,016,328 issued Jan. 9, 1962 to Rollin E. Pepper et al and assigned to Ethicon, Inc., discloses a sterilizing agent which is an aqueous solution of glutaraldehyde having an alkaline pH, generally around 7.5 to 8.0. This alkaline composition is effective in killing dormant spores at temperatures of around 20.degree. to 25.degree. C. in treatment periods of from 3 to 10 hours to achieve complete deactivation depending on the state and resistance of the spores.
While acid aqueous solutions of glutaraldehyde are stable and have long shelf life, alkaline solutions by contrast tend to lose their sporicidal activity rapidly upon storage, as a result, it is thought, of alkaline catalyzed polymerization of the glutaraldehyde. This latter defect has lead to the marketing of the product in the form of an aqueous acid solution of glutaraldehyde together with a separate container of solid alkali, such as, sodium bicarbonate, the alkali being added to the acid solution just prior to use to provide the required alkaline pH.
This procedure gives rise to several problems. Thus, the container of alkali may become detached from the container of aqueous glutaraldehyde. Alternatively, the addition of alkali may be accidentally omitted by the user. In either case, this leads to the use of a solution known to be ineffective at 20.degree. to 25.degree. C. in an acceptable period of time (i.e., less than 16 hours).
In view of the prior art problems associated with the use of alkaline glutaraldehyde solutions, various prior attempts have been made to provide acid glutaraldehyde solutions having sporicidal activity and thereby take advantage of the stable nature of acid glutaraldehyde.
For example, U.S. Pat. No. 3,282,775 (Stonehill) describes glutaraldehyde compositions including acid glutaraldehyde compositions, containing cationic surfactants and U.S. Pat. No. 3,912,450 (Boucher) describes acid glutaraldehyde compositions containing certain non-ionic surfactants.
Further, in U.S. Pat. No. 3,647,222 (Sierra), it is suggested to heat acid glutaraldehyde to a temperature above about 45.degree. C. or to effect sterilization using acid glutaraldehyde solution in the presence of ultrasonic energy both at ambient and elevated temperatures.